X-ray diagnosis apparatus

ABSTRACT

In a storing unit of a medical image processing apparatus, first 3D image corresponding to a first period and second 3D image data corresponding to a second period are stored. The first 3D image data corresponds to a period before contrast agent injection operation and/or therapeutic operation. The second 3D image data corresponds to a period after the contrast agent injection operation and/or therapeutic operation. A 3D subtracting unit subtracts the first 3D image data from the second 3D image data. In 3D subtraction image data, a portion having undergone a change due to contrast agent injection operation and/or therapeutic operation is emphasized. A pseudo 3D image data generating unit generates pseudo 3D image data on the basis of 3D subtraction image data. A displaying unit displays the pseudo 3D image data.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a medical image processingapparatus for supporting an examination, diagnosis, and therapy using acatheter and the like.

[0002] According to a conventional therapeutic method for aneurysms, anincision is surgically made in a patient's body to expose a morbidportion (aneurysm), and the neck of the exposed aneurysm is fastenedwith a clip to prevent blood from flowing into the aneurysm.

[0003] Recently, however, a great deal of attention has been given to alow-invasive therapeutic method represented by IVR (InterVentionalRadiology). The low-invasive therapeutic method is also applied to atherapy for aneurysms. For example, a catheter is inserted into apatient's body from the groin to an aneurysm through a blood vessel.This operation is performed with a guide of a blood vessel image (to bereferred to as a “contrast image” hereinafter) whose contrast isenhanced by a contrast agent. When the catheter reaches the aneurysm, acoil-like occlusive material 200 shown in FIG. 1 is injected from thedistal end of the catheter into the aneurysm to fill the aneurysm withthe occlusive material 200. The blood then stagnates in the aneurysmfilled with the occlusive material 200. The stagnant blood coagulatesafter a while. With this operation, a therapeutic effect similar to thatof a clip therapy can be obtained.

[0004] There are various occlusive materials 200 with differentmaterials, shapes, sizes, and the like. Selecting the occlusive material200 having a suitable size for the size of the internal portion of theaneurysm is important to attain a desired therapeutic effect. Tothree-dimensionally grasp the size of the internal portion of theaneurysm, a plurality of blood vessel extraction images acquired by DSM(Digital Subtraction Angiography) at a plurality of projection anglesare used.

[0005] Such blood vessel extraction images are acquired after a surgicaloperation. A therapeutic effect is checked by comparing these bloodvessel extraction images after the surgical operation with thoseacquired before the surgical operation. In general, to improve theprecision of this therapeutic effect check, blood vessel extractionimages are acquired after a surgical operation at the same projectionangles as those before the surgical operation.

[0006] As described above, contrast images and blood vessel extractionimages acquired at a plurality of projection angles are very effectivein grasping the 3D structure of a target.

[0007] The power of expression of contrast images and blood vesselextraction images is not sufficient to grasp the complicated structureof a blood vessel. For this reason, it may take much time to move acatheter to a target. In addition, it may take much time to search foroptimal projection angles, or radiography may need to be repeated manytimes at various projection angles to obtain detailed depth information.

[0008] Furthermore, blood vessel extraction images are acquired to checkan occlusive material therapy and medical therapeutic effect in acatheter therapy. To perform this check, images of the aneurysm andnearby portions are required, but images of portions outside them arenot required. In this case, X-rays with which these outside portions areirradiated will cause unnecessary exposure to X-rays.

BRIEF SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide an imagewhich effectively supports an operator in grasping the 3D structure of ablood vessel in a medical image processing apparatus.

[0010] According to the present invention, in a medical image processingapparatus, a storing unit stores first 3D image data corresponding to afirst period and second 3D image data corresponding to a second period.The first 3D image data corresponds a period before condition changing.The second 3D image data corresponds to a period after conditionchanging. A 3D subtracting unit subtracts the first 3D image data fromthe second 3D image data. In 3D subtraction image data, a portion thathas changed due to the condition changing is emphasized. The pseudo 3Dimage data generating unit generates pseudo 3D image data on the basisof the 3D subtraction image data. A display unit displays pseudo 3Dimage data.

[0011] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0012] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate presently preferredembodiments of the invention, and together with the general descriptiongiven above and the detailed description of the preferred embodimentsgiven below, serve to explain the principles of the invention.

[0013]FIG. 1 a schematic view showing an occlusive material (coil)detained in an aneurysm to perform therapy for the aneurysm;

[0014]FIG. 2 is a block diagram showing the arrangement of an X-raydiagnosis apparatus for the circulatory system according to the firstembodiment of the present invention;

[0015]FIG. 3 is a view showing a plurality of types of images that canbe generated in this embodiment and procedures for processing theimages;

[0016]FIG. 4 is a view showing a plurality of types of images that canbe generated in this embodiment and procedures for processing theimages;

[0017]FIG. 5A is a view showing the maximum irradiation range in thisembodiment;

[0018]FIG. 5B is a view showing the reduced irradiation range in thisembodiment;

[0019]FIG. 6A is a schematic view showing a distorted image in thisembodiment;

[0020]FIG. 6B is a schematic view showing a distortion-corrected imagein this embodiment;

[0021]FIG. 7 is a view showing a rotational center aligned with thecenter of an ROI in the first modification of this embodiment;

[0022]FIG. 8 is a block diagram showing a reduction processing unitprovided to reduce the amount of 3D image generation processing for ROIsetting in the second modification of this embodiment;

[0023]FIG. 9 is a block diagram showing an ROI setting unit for settingan ROI by using a plurality of images obtained at different projectionangles in the third modification of this embodiment;

[0024]FIG. 10A is a view for supplementing the description of ROIsetting in FIG. 9;

[0025]FIG. 10B is a view for supplementing the description of ROIsetting in FIG. 9;

[0026]FIG. 11 is a block diagram showing the arrangement of an X-raydiagnosis apparatus for the circulatory system according to the secondembodiment of the present invention;

[0027]FIG. 12 is a block diagram showing the arrangement of an X-raydiagnosis apparatus for the circulatory system according to the thirdembodiment of the present invention; and

[0028]FIG. 13 is a block diagram showing the arrangement of an X-raydiagnosis apparatus having a biplane arrangement according tomodifications of the third embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0029] An image processing display apparatus according to eachembodiment of the present invention will be described below withreference to the views of the accompanying drawing. The image processingdisplay apparatus according to the present invention includes a modalitycapable of acquiring 3D images, e.g., an X-ray diagnosis apparatus,ultrasonic diagnosis apparatus, X-ray computer tomography apparatus(X-ray CT), magnetic resonance imaging apparatus (MRI), or nuclearmagnetic diagnosis apparatus (SPECT, PET). Recently, 3D (threedimensional) image is obtain used for diagnosing and treating. In thiscase, 3D images having various information are generated. For example,an X-ray diagnosis apparatus, and more specifically, an X-ray diagnosisapparatus for the circulatory system, will be described below as animage processing display apparatus.

[0030] [First Embodiment]

[0031] As shown in FIG. 2, the X-ray diagnosis apparatus according tothe first embodiment has a radiography unit 1. The radiography unit 1includes an arcuated arm 14 capable of rotating about three axesincluding the body axis of a subject, an X-ray tube 12 mounted on oneend of the arcuated arm 14, an X-ray collimator 16 mounted in the X-raywindow of the X-ray tube 12, and a camera system 13 mounted on the otherend of the arcuated arm 14. For the sake of descriptive convenience, arotational angle about the body axis of the subject corresponds to aprojection angle. This projection angle data is stored in a projectionangle memory 3. The camera system 13 is comprised of an imageintensifier, optical system, and TV camera. The camera system 13 may bea planar X-ray detector constituted by solid image sensing elements,each having a scintillator and photodiode, arrayed in the form of amatrix.

[0032] An A/D converter 2 converts an analog video signal output fromthe camera system 13 into a digital signal. A 2D/3D image data storingunit 6 is configured to store 2D and 3D image data to be processed inthis system, including this converted 2D image data (original 2D imagedata).

[0033] A subtracting unit 4, adding unit 17, reconstructing unit 5, anddistortion correcting unit 18 are mutually connected to the 2D/3D imagedata storing unit 6. The reconstructing unit 5 is configured toreconstruct 3D image data from multiangle 2D image data (original 2Dimage data or 2D subtraction image data) stored in the 2D/3D image datastoring-unit 6. This 3D image data may be binary data or gray-leveldata. For image reconstruction processing, for example, the weightcorrecting filtered-backprojection method proposed by Feldkamp et al. isused.

[0034] The subtracting unit 4 is configured to subtract two 2D imagedata (original 2D image data or 2D subtraction image data) stored in the2D/3D image data storing unit 6 or subtract two 3D image data stored inthe 2D/3D image data storing unit 6. The adding unit 17 is configured toadd two 3D image data stored in the 2D/3D image data storing unit 6.Note that target image data to be subjected to reconstructionprocessing, subtraction processing, and addition processing can bearbitrarily selected from the image data stored in the 2D/3D image datastoring unit 6 in accordance with a user instruction.

[0035] A pseudo 3D image data generating unit 15 is configured togenerate pseudo 3D image data such as surface image and projection imagedata for stereoscopically displaying a target on a 2D screen from 3Dimage data stored in the 2D/3D image data storing unit 6. A comparingunit 7 is configured to unify display parameters such as luminance toallow two or more pseudo 3D image data to be easily compared with eachother. The image data generated by these units 15 and 7 are sent to adisplaying unit 8 through a D/A converter 9.

[0036] A ROI setting unit 10 is configured to allow the operator to seta region of interest (ROI) on the image displayed on the displaying unit8. A collimater/bed controller 11 adjusts the aperture of the X-raycollimator 16 and changes the position of the bed in accordance with theset region of interest.

[0037] The operation of the first embodiment will be described next.

[0038]FIG. 3 shows the temporal relationship between various events andradiographic operation. FIG. 3 shows various 2D and 3D image data thatcan be generated, together with the flow of corresponding processes(subtraction processes, addition processes, and reconstructionprocesses).

[0039] As events, the therapeutic operation for an aneurysm in FIG. 1and contrast agent injection operation are assumed. At least tworadiographic operations are performed before the therapeutic operation.One radiographic operation is performed before a contrast agentinjection operation. The other radiographic operation is performed afterthe contrast agent injection operation. Original multiangle 2D imagedata (A, B) that can be used for reconstruction processing of 3D imagedata are acquired by the two radiographic operations. Each multiangle 2Dimage data includes, for example, 120 images acquired at projectionangle intervals of 3°.

[0040] Similarly, at least two radiographic operations are performedafter the therapeutic operation. One radiographic operation is performedbefore a contrast agent injection operation. The other radiographicoperation is performed after the contrast agent injection operation.Original multiangle 2D image data (C, D) that can be used forreconstruction processing of 3D image data are acquired by the tworadiographic operations. The multiangle 2D image data (A, B, C, D) arestored in the 2D/3D image data storing unit 6.

[0041] The subtracting unit 4 subtracts 2D image data (A) beforecontrast agent injection from 2D image data (B) after contrast agentinjection in units of projection angles to obtain multiangle 2Dsubtraction image data (E) before a therapy. This 2D image data (E) isstored in the 2D/3D image data storing unit 6. In this 2D image data(E), a blood vessel and an aneurysm before a therapy are emphasized.

[0042] The subtracting unit 4 subtracts 2D image data (C) beforecontrast agent injection from 2D image data (D) after contrast agentinjection in units of projection angles to obtain multiangle 2Dsubtraction image data (I) after the therapy. This 2D image data (I) isstored in the 2D/3D image data storing unit 6. In this 2D image data(I), the blood vessel and the aneurysm after the therapy are emphasized.

[0043] The subtracting unit 4 subtracts the multiangle 2D image data (A)before the therapy and contrast agent injection from the multiangle 2Dimage data (C) after the therapy and contrast agent injection in unitsof projection angles to obtain multiangle 2D subtraction image data (F).This 2D image data (F) is stored in the 2D/3D image data storing unit 6.In the 2D image data (F), a coil detained in the aneurysm by thetherapeutic operation is emphasized.

[0044] The subtracting unit 4 subtracts the multiangle 2D image data (D)before the therapy and contrast agent injection from the multiangle 2Dimage data (D) in units of projection angles to obtain multiangle 2Dsubtraction image data (G). This 2D image data (G) is stored in the2D/3D image data storing unit 6. In this 2D image data (G), the bloodvessel, aneurysm after the therapy, and coil detained in the aneurysmare emphasized.

[0045] The subtracting unit 4 subtracts the multiangle 2D image data (B)before the therapy and after contrast agent injection from themultiangle 2D image data (D) after the therapy and contrast agentinjection in units of projection angles to obtain multiangle 2Dsubtraction image data (H). This 2D image data (H) is stored in the2D/3D image data storing unit 6. In the 2D image data (H), a changedportion between the aneurysm before the therapy and the aneurysm afterthe therapy is emphasized.

[0046] The reconstructing unit 5 converts the multiangle 2D subtractionimage data (E, F, G, H, I) into 3D image data (J, K, L, M, N) byperforming reconstruction processing and referring to the 3D image datausing parameters such as the SID (the distance from the focal point ofthe X-ray tube 12 to the detector 13), radiographic mode, and projectionangle which are stored in the projection angle memory 3. The 3D imagedata (J, K, L, M, N) are stored in the 2D/3D image data storing unit 6.Note that a reconstruction region is defined as a cylinder inscribed inan X-ray beam irradiated from the X-ray tube 12 in all directions. Theinternal portion of this cylinder must be divided into 3D discretesegments on the basis of a length d of a central portion of areconstruction region projected on the width of one detection element ofthe detector 13, and a reconstructed image must be obtained from data ofthe discretion points. This discretion interval is an example and maychange depending on the apparatus and maker. Basically, therefore, thediscretion interval defined by each apparatus may be used. According tothe Feldkamp method as a reconstruction method, for example, anappropriate convolution filter like the one used by Shepp & Logan orRamachandran is applied to 120 2D images, and a 3D inverse projectioncomputation is performed while multiplying the resultant data by acoefficient for correcting the 3D spread of a beam, thereby forming a 3Dimage.

[0047] The subtracting unit 4 subtracts 3D image data (N) from 3D imagedata (J) to obtain 3D subtraction image data (P) that allows theoperator to check a therapeutic effect.

[0048] The adding unit 17 adds 3D image data (K) to 3D image data (J) toacquire addition 3D image data (O) that allows the operator to check thestate of the coil detained in the aneurysm by the therapeutic operation.If the operator recognizes from the addition 3D image data (O) theconditions of the coil and the aneurysm, he/she performs a therapeuticoperation again.

[0049] The adding unit 17 adds the 3D image data (K) to the 3D imagedata (N) to acquire addition 3D image data (Q) that allows the operatorto check the state of the coil detained in the aneurysm by thetherapeutic operation. If the operator recognizes from the addition 3Dimage data (Q) the conditions of the coil and the aneurysm, he/sheperforms a therapeutic operation again.

[0050] As shown in FIG. 4, the 3D image data (J, K, L, M, N) may beacquired by converting the multiangle original 2D image data (A, B, C,D) into 3D image data (A′, B′, C′, D′) by reconstruction processing, andperforming 3D subtraction processing using 3D image data (A′, B′, C′,D′).

[0051] Various clinically useful 2D and 3D image data can be acquired byarbitrarily and selectively using reconstruction processing, 2Dsubtraction processing, 3D subtraction processing, 2D additionprocessing, and 3D addition processing in this manner.

[0052] The pseudo 3D image data generating unit 15 extracts the surfaceshapes of the blood vessel and aneurysm, by threshold processing, fromthe 3D image data (J to Q) selectively read out from the 2D/3D imagedata storing unit 6 in accordance with a user instruction, and performsshading on the basis of the surface shapes and depth information,thereby generating pseudo 3D image data (a 2D image looks like a 3Dimage) of the blood vessel and aneurysm observed from an arbitrarydirection. This pseudo 3D image data is supplied to the displaying unit8 through the D/A converter 9. As a consequence, a pseudo 3D image ofthe blood vessel and aneurysm observed from an arbitrary direction isdisplayed on the displaying unit 8.

[0053] In this case, surface rendering is used as a stereoscopic displaymethod. However, the present invention is not limited to this, and otherpseudo 3D image display methods such as volume rendering may be used.

[0054] A region of interest (ROI) including the aneurysm is set throughthe ROI setting unit 10 on the image of the blood vessel and aneurysmdisplayed on the displaying unit 8. For example, the ROI setting unit 10is an input unit such as a mouse device, track ball, or keyboard. TheROI setting unit 10 is configured to set an ROI by designating thecentral position of the ROI and its radius.

[0055] More specifically, the operator designates a position regarded asthe center of the aneurysm with the mouse device. A straight lineexpression is obtained from the designated position in a directionperpendicular to the image. A search for a 3D image is sequentially madeon a pixel-width basis along this straight line, and a coordinate valueA of a position at which a detected value exceeds the threshold first isstored. The search is continued to store a coordinate value B of aposition at which a detected value becomes smaller than the threshold.The midpoint between the positions A and B is set as the center of theaneurysm.

[0056] A method of obtaining the center of an aneurysm is not limited tothis method. For example, after a straight line expression is obtainedfrom the position designated with the mouse device in a directionperpendicular to the image, similar processing is performed for an imageobserved at another angle, and the intersection of the obtained straightlines (in practice, the midpoint between points on the straight lineswhich approach most) may be obtained as the center of the aneurysm. Inaddition, the radius may be input with the keyboard, and a circleindicating the ROI, which is drawn on the image, may be enlarged/reducedwith the mouse. In this case, the ROI is assumed to be a sphere.However, the ROI may have another shape. In addition, the display colorof a portion in the ROI may be changed, or its display density may beinverted. Alternatively, a dot or stripe pattern may be pasted on theROI. This facilitates recognition of the range of a set ROI. When theROI is set in this manner, the ROI setting unit 10 supplies the ROIinformation (center and radius) to the collimater/bed controller 11.

[0057] The collimater/bed controller 11 adjusts the aperture of theX-ray collimator 16 to irradiate only a region of the subject whichcorresponds to the ROI with X-rays at various projection angles on thebasis of the information of the set ROI. Consider the case shown inFIGS. 5A and 5B. Before coil detaining, as shown in FIG. 5A, theaperture of the X-ray collimator 16 is widened to radiograph the overallblood vessel and aneurysm. When the ROI shown in FIG. 5B is set with theROI setting unit 10, the aperture of the X-ray collimator 16 is narrowedto make an X-ray beam circumscribe the spherical ROI. The dataindicating the aperture for each projection angle which is determined inthis manner is used for multiangle radiographic operation (to bedescribed below) after coil detaining.

[0058] Radiographic operation after coil detaining will be describednext. After coil detaining, two sets of 120 2D images (C, D) areacquired at projection angle intervals of 3° by multiangle radiographicoperation before contrast agent injection and multiangle radiographicoperation after contrast agent injection. In this radiographicoperation, the aperture is changed to irradiate only the ROI with X-rayson the basis of aperture data from the collimater/bed controller 11, andradiography is repeated, as shown in FIG. 5B. The image data obtained bythis radiographic operation is A/D-converted, and the resultant data isstored in the 2D/3D image data storing unit 6.

[0059] The subtracting unit 4 subtracts each pair of images, of theimages (C, D) acquired beforelafter contrast agent injection and storedin the 2D/3D image data storing unit 6, which are radiographed at thesame projection angle from each other, and supplies the resultantsubtraction image to the reconstructing unit 5. Subtraction processingis performed only within the projection region of the ROI. Other regionsare handled as regions with no value. If, however, a blood vesselextends in a direction perpendicular to the rotational axis, andprojection extends outside the ROI, a contrast-enhanced image valuebefore coil detaining may be set outside the projection region of theROI.

[0060] The first set of radiographic images supplied to the subtractingunit 4 includes contrast images (contrast-enhanced images) and maskimages (non-contrast-enhanced images) before and after coil detaining.The reconstructing unit 5 form a 3D image of only the ROI on the basisof these subtraction images as in the above case. With this operation,an image (I) of the blood vessel and aneurysm with little blood isreconstructed. This image (I) is temporarily stored in the 2D/3D imagedata storing unit 6.

[0061] The next set of radiographic images supplied to the subtractingunit 4 includes mask images (C) after coil detaining and mask images (A)before coil detaining. The reconstructing unit 5 generates a 3D image ofonly the ROI on the basis of these subtraction images (G) as in theabove case. With this operation, a 3D image (K) indicating thedistribution of the coil (occlusive material) is generated. This 3Dimage (K) is also temporarily stored in the 2D/3D image data storingunit 6.

[0062] The operation of the comparing unit 7 will be described next. Thecomparing unit 7 unifies display parameters such as luminance tofacilitate comparison between two or more pseudo 3D image data selectedin accordance with a user instruction. The comparing unit 7 alsoarranges and displays two or more pseudo 3D image data with unifieddisplay parameters on one screen. Observing the arranged images, theobserver can accurately grasp a change in blood flow before and aftercoil detaining, i.e., a therapeutic effect. Note that a plurality ofpseudo 3D images may be displayed within the same area. This makes itpossible to observe changes in the two images in a small display area.The pseudo 3D images may be simultaneously displayed in differentcolors. This makes it easier to recognize changes in the two images. Inthis case, overlapping portions of the pseudo 3D images may besimultaneously displayed or one of them may be preferentially displayed.This preferential image switching can be easily performed by designatingwith a user instruction.

[0063] When the pseudo 3D image data generating unit 15 is to generate apseudo 3D image, not only information about a structure but also itsdensity information may be simultaneously displayed. This makes iteasier to recognize changes in the two images. If, for example, theinformation about the structure is displayed with luminance as before,and the density information is displayed in color, the two pieces ofinformation can be grasped at once.

[0064] In addition, when at least two sets of pseudo 3D images generatedby the pseudo 3D image data generating unit 15 are to be displayed, theymay be rotated while being synchronized angularly. This allows theoperator to observe the respective images at the same angles.

[0065] A case wherein a 3D image (J or N) and 3D image (L) are selectedwill be described next. The unit 15 generates pseudo 3D images observedfrom various directions on the basis of the 3D image (J or N) and 3Dimage (L), and supplies them to the comparing unit 7.

[0066] The adding unit 17 adds the 3D image (J or N) and 3D image (L) toobtain one image (O or Q), and supplies it to the displaying unit 8through the D/A converter 9. At this time, the unit 15 uses the centercoordinates of the ROI, which are obtained by the ROI setting unit 10 inadvance, to obtain a plane that is perpendicular to the observationdirection and passes through the center coordinates, and erases datalocated before the plane. This makes it possible to observe the state ofthe coil detained in the aneurysm from all directions, thus facilitatinga check on the effect of the occluding operation and selection of anocclusive material to be detained in the aneurysm again.

[0067] In this case, if the camera system 13 is made up of an imageintensifier, optical system, and TV camera, 2D images distort. If a meshpattern in the form of a square lattice is radiographed by the imageintensifier, a distortion occurs, as shown in FIG. 6A. This is because,the I.I. has a spherical X-ray detection surface, and the detected imageundergoes a pincushion distortion. In addition, the track of an electronbeam bends due to the influence of magnetism such as geomagnetism,resulting in an s-shaped distortion. A corrected image corresponding toarbitrary position coordinates (id, jd) in FIG. 6A should be arranged atpredetermined intervals two-dimensionally from the center. Assume thatthe corresponding position coordinates of the corrected image are (i,j). That is, (id, jd) and (i, j) respectively represent imagecoordinates on the acquired image and distortion-corrected image. Theimage coordinate system is a coordinate system having an upper leftpoint on the image as an origin, an upper right point represented by(N−1, 0), an upper left point represented by (0, N−1), and a lower rightpoint represented by (N−1, N−1). N represents the matrix size of theimage. In general, N=512 or 1,204 [pixel]. The distortion of an I.I.image can be corrected by substituting the data of (i, j) on thecorrected image for the data of (id, jd) on the acquired image.

[0068] The relationship between (i, j) and (id, jd) is determined by thelocation of the apparatus, projection angle, SID, and image intensifiersize. This relationship slightly varies depending on the imageintensifier to be used even if these conditions remain unchanged. Therelationship between (i, j) and (id, jd) must therefore be grasped inadvance under the respective conditions for each image intensifier to beused. In general, this relationship can be empirically obtained.

[0069] For example, a grid is bonded on the front surface of the imageintensifier, and the grid is radiographed at each angle required for anexamination to obtain the positions of grid points (intersections ofwires) from the grid projection image. These grid points should bearranged at equal intervals two-dimensionally on the image if nodistortion occurs. If, therefore, the grid points are rearranged,centered on the grid point nearest to the center of the image, at knowninter-grid-point intervals, the image distortion is corrected. Inaddition, the positions of points other than the grid points can beapproximately obtained on the basis of the positions of the surroundinggrid points. The distortion correction unit performs such operation ateach projection angle. With this distortion correcting unit 18, adisplayed image without any distortion can be obtained even by using animage intensifier. This allows the operator to accurately observe atarget therapy portion or the like.

[0070] [First Modification of First Embodiment]

[0071] After an ROI is set with the ROI setting unit 10, the controller11 may control the bed and radiography unit 1 as well as the X-raycollimator 16 to move them to position a center P of the ROI to thecenter of the camera system 13 at all projection angles, as shown inFIG. 7. In this case, since the collimater 16 is controlled around thecenter O of the camera system 13 symmetrically in the vertical andhorizontal directions, control of the collimater 16 can be facilitated.

[0072] [Second Modification of First Embodiment]

[0073] In the first embodiment, although an ROI is set on the basis of a3D image, the amount of processing for reconstruction is enormous. Evenif, for example, an apparatus designed specifically for reconstructionis used, it takes about six min to process 256×256×256 [pixel3]. Ittakes 384 min (6.4 hrs) or 3,072 min (51.2 hrs) to obtain a 3D imagewith a resolution of 1024×1024×1024 [pixel3] or 2048×2048×2048 [pixels]from image data acquired with a resolution of 1024×1024 [pixel2] or2048×2048 [pixel2] by using an apparatus with the same reconstructionspeed as that of the above apparatus. In addition, it takes 48 min toobtain a 3D image with a resolution of 512×512×512 [pixel3] even on thebasis of acquired image data with a resolution of 512×512 [pixel2]. Thisreconstruction time is very long as compared with the time intervalbetween the instant at which radiographic operation before coildetaining is complete and the instant at which multiangle radiographicoperation is performed after the coil is detained. That is, thistechnique is not practical.

[0074] As shown in FIG. 8, therefore, an image reducing unit 20 isconnected to the output stage of the subtracting unit 4, and asubtraction image (or a distortion-corrected image from the distortioncorrecting unit 18) is reduced in image reconstruction before coildetaining to perform reconstruction processing in the reconstructingunit 5 on the basis of the image reduced by this reduction processing.For example, image data of 1024×1024 [pixel2] is reduced to 256×256[pixel2] or 128×128 [pixel2], and the reconstructing unit 5 performsimage reconstruction processing on the basis of the reduced data.

[0075] This operation can greatly decrease the amount of processing tobe performed by the X-ray diagnosis apparatus in the interval betweenthe instant at which radiographic operation before coil detaining iscomplete and the instant at which multiangle radiographic operation isperformed again after an occlusive material is detained. The X-raydiagnosis apparatus can therefore finish setting an opening and bedposition until the next multiangle radiographic operation.

[0076] Although the resolution of an image observed in ROI settingoperation decreases due to this reduction processing, a 3D image formedfrom reduced image data is sufficient for this ROI setting operationbecause it is only required that the position and size of an aneurysm beapproximately grasped. However, a 3D image (1) of only an ROI must bereconstructed again. This ROI image is preferably reconstructedimmediately after ROI setting. At this time, it is preferable that theabove reduction processing is not performed. Note that the above 3Dimage (N) and 3D image (P) are reconstructed after an occlusive materialis detained and multiply operation radiographic operation is performed.

[0077] [Third Modification of the First Embodiment]

[0078] In the second modification described above, the processing timein setting an ROI is shortened at the expense of the resolution of a 3Dimage. An ROI may be set on the basis of two or more images radiographedat different projection angles. FIG. 9 shows an apparatus arrangementfor this operation.

[0079] Referring to FIG. 9, an aneurysm is radiographed from twodirections first, and then the radiographic images are converted intodigital signals by the A/D converter 2 and supplied to an ROI settingunit 21. In this case, if a biplane system having two pairs of X-raytubes 12 and camera systems 13 is used, target images can be obtained byone radiographic operation.

[0080] The ROI setting unit 21 supplies the images to the displayingunit 8 through the D/A converter 9. If, for example, the frontal image(Frontal) shown in FIG. 10A and the lateral image (Lateral) shown inFIG. 10B are displayed on the displaying unit 8, an ROI (center andradius) is set on each displayed image.

[0081] More specifically, a point K regarded as the center of ananeurysm is designated on one (in this case, for example, the frontalimage) of the images (FIG. 10A). The ROI setting unit 21 computes astraight line (epipolar line) like the one indicated by the dotted linein FIG. 10B which connects the point K and the focus of the X-ray tube12, and projects this line on the X-ray tube 12 on the opposite side(the lateral image side in this case). This projected straight lineimage is superimposed on the image.

[0082] Since the center of the aneurysm should be located on theepipolar line, a central point H shown in FIG. 10B is designated on thisline. As in the above case, the ROI setting unit 21 computes a straightline that connects the point H and the focal point of the X-ray tube 12,and determines the intersection of the two straight lines as the centralpoint of the ROI. These straight lines may not intersect. In such acase, the midpoint between the nearest points is obtained as the centerof the ROI. A radius is designated on either the frontal image or thelateral image. An ROI is determined by correcting the radius inconsideration of the geometrical magnification of X-rays.

[0083] When the ROI information is supplied from the ROI setting unit 21to the collimater/bed controller 11, the collimater/bed controller 11determines the aperture of the X-ray collimator 16 or the position ofthe bed or radiography system at an arbitrary projection angle on thebasis of the ROI information.

[0084] More specifically, the bed or radiography unit 1 is moved toalways locate the center of the ROI at the center of the camera system13 during multiangle radiographic operation, as described with referenceto FIG. 7. In addition, the X-ray collimator 16 is ON/OFF-controlled toirradiate only the ROI with X-rays. By radiographing only the ROIregion, only the ROI is irradiated with X-rays even during multiangleradiographic operation before an occlusive material is detained. Thismakes it possible to reduce the excess dose of radiation to which thesubject is exposed.

[0085] (Second Embodiment)

[0086] An X-ray diagnosis apparatus according to the second embodimentof the present invention will be described next. The same referencenumerals as in the second embodiment denote the same parts in the firstembodiment, and a description thereof will be omitted.

[0087] As shown in FIG. 11, the X-ray diagnosis apparatus according tothe second embodiment includes a radiography unit 1 for performingradiographic operation, an A/D converter 2 for digitizing a video signalsupplied as analog information from the radiography unit 1, a memory 3for storing radiographic conditions from the radiography unit 1, ageometry processing unit 30 for converting image data into a readableimage, a gray-level converting unit 31, an edge enhancing unit 32, and aD/A converter 33 for converting the image data generated by theseprocessing units 30, 31, and 32 into an analog signal to be displayed ona displaying unit 34.

[0088] The geometry processing unit 30 performs linear conversion forenlargement, rotation, movement, and the like. If a camera system 13includes an image intensifier, the geometry processing unit 30 performsdistortion correction processing.

[0089] The gray-level converting unit 31 adjusts display density toallow a target structure to be easily seen. The edge enhancing unit 32performs edge emphasis processing by using a high-frequency emphasisfilter (edge emphasis filter) such as a Laplacian or differentialfilter. The degree of each processing can be changed step by step by aninput device (not shown), and each processing can be selectivelyexecuted.

[0090] The images acquired by the camera system 13 are A/D-converted bythe A/D converter 2 and stored in an image data storing unit 6. Inaddition to the 2D images acquired by the X-ray diagnosis apparatus forthe circulatory system, this image memory 6 stores the 3D imagesreconstructed by other modalities such as an X-ray CT apparatus 36,nuclear magnetic resonance apparatus 37 (MRI), and SPECT apparatus 38connected to the X-ray diagnosis apparatus through a bus line 35, or the3D images obtained by a 3D CT apparatus 39 such as an X-ray system forthe circulatory system or similar system described in the firstembodiment.

[0091] A projection converting unit 40 converts these 3D images intoprojection images at angles and positions coinciding with those of thecurrently radiographed image on the basis of the radiographic conditionssupplied from the radiography unit 1 and recorded on the projectionangle memory 3 in each radiographic operation. A D/A converter 41converts these projection images into analog signals to be displayed ona displaying unit 42.

[0092] Although the second embodiment includes the two displaying units,i.e., the displaying unit 34 and displaying unit 42, this apparatus mayinclude one of these displaying units. In this case, radiographic andprojection images are displayed to be juxtaposed or superimposed.

[0093] The operation of the second embodiment having this arrangementwill be described next. In the second embodiment, first of all, theapparatus is operated while the operator moves a catheter to a morbidportion under fluoroscopic observation (radiographic operation with alow dose of radiation without injecting any contrast agent). In such acase, the operator cannot move the catheter forward unless he/she graspsblood vessel running. This is true especially when the blood vessel hasa complicated structure. In general, therefore, before the operatormoves the catheter forward, a contrast agent is injected to radiographthe blood vessel, and the contrast-enhanced image (still image) isdisplayed to be juxtaposed to the radiographed image (moving image:currently radiographed image) or superimposed thereon. With thisoperation, the operator can always grasp the blood vessel runningwithout injecting any contrast agent. The examiner (operator) moves thecatheter forward on the basis of the contrast-enhanced image (using thecontrast-enhanced image as a guide). This contrast-enhanced image iscalled a road map. To generate a road map, however, radiographicoperation must be performed with a contrast agent and a relatively largedose of radiation.

[0094] In the second embodiment, therefore, the projection convertingunit 40 performs 3D projection conversion processing on the basis of a3D image such as a CT image, MRI image, 3D image, or CT image which isobtained in advance by radiographing the same subject and the currentradiographic conditions (SID, projection angle, radiographic mode,projection position, and the like). The resultant data is then providedas a road map through the D/A converter 41 and displaying unit 42. Thisprojection conversion processing is performed every time the projectionangle and position change. This makes it possible to reduce the amountof contrast agent and the dose of radiation which are used to generate aroad map.

[0095] At this time, the projection converting unit 40 extracts a bloodvessel portion from the CT image, MRI image, 3D image, CT image, or thelike by threshold processing, and projects only the extracted bloodvessel. If extraction is difficult to perform with a simple threshold,an interactive region-growing method may be used. Projection isperformed while the values in the blood vessel which are extracted inthis manner are replaced with arbitrary absorption coefficients, and theabsorption coefficients in other portions are set to 0, therebygenerating a projection image like a DSA image. A CT image, 3D image, orCT image reconstructed from DSA image data is directly subjected toprojection conversion.

[0096] A projection angle offset with respect to the patient due to themovement of the patient between acquisition of 3D images and catheterinsertion can be corrected by using three or more markers reflected inthe 3D image and radiographic images observed from two or moredirections. Such a marker may be one that has a high absorptioncoefficient and pasted on the body surface or a characteristic structureinside the body, e.g., a branch of the blood vessel. More specifically,if three or more markers can be specified on the 3D image andradiographic images observed from two or more directions, thecoordinates of the three markers within the coordinate system defined bythe 3D image and the coordinates within the coordinate system defined bythe radiography system can be calculated. The above correction can beperformed by obtaining the rotational angle of the 3D image in which thethree markers coincide with each other. Such operation of obtaining acorrection angle may be performed once before a road map is generated.In this case, although only the angles are made to coincide with eachother, positions may also be made to coincide with each other.

[0097] [Modification of Second Embodiment]

[0098] In the second embodiment described above, a road map is generatedevery time the projection angle changes. In a region where a change inprojection angle (translation) is small, a road map may be translated inaccordance with a change in projection angle. In addition, in a regionwhere a change in projection angle is small, since a change in load mapwith a change in angle is small as compared with a change in road mapwith position movement, a change in projection angle can be properlycoped with to a certain degree without changing a road map. A road mapis therefore computed and generated again only when the projectionposition or angle at which the previous road map was generated changesbeyond a predetermined range. In a region where a change in projectionposition or angle is small, a change in projection angle can be properlycoped with by the previous road map without generating any new road map.

[0099] [Third Embodiment]

[0100] An X-ray diagnosis apparatus according to the third embodiment ofthe present invention will be described next. The same referencenumerals as in the first and second embodiments denote the same parts inthe third embodiment, and a detailed description thereof will beomitted. When a road map is generated according to the procedure in thesecond embodiment, blood vessels overlap depending on the projectionangle. This may make it difficult to identify a target blood vesselstructure. The third embodiment is made to solve this problem.

[0101]FIG. 12 shows the apparatus arrangement of the third embodiment,in which a pseudo 3D image data generating unit 50 extracts a targetregion from the 3D image data stored in an image memory 6 by the abovesimple threshold processing, region-growing method, or the like. Thesurface structure is then shaded. The resultant data is converted intoan analog signal by D/A converter 52 to be displayed on a displayingunit 53. By observing this pseudo 3D image from various directions, theoperator can grasp the 3D structure of the target region.

[0102] The operator then sets an ROI on this pseudo image using an ROIsetting unit 51 in the same manner as in the first embodiment. When anROI is set, the ROI setting unit 51 displays the ROI upon making itreadable by changing the color of the internal portion of the ROI. Inthis case, the ROI is regarded as a spherical region. However, an ROIhaving a shape other than a spherical shape may be set. Alternatively, aplurality of ROIs may be designated. If a plurality of ROIs aredesignated, a final ROI is determined as an overlap of these ROIs.

[0103] The ROI information set by the ROI setting unit 51 is supplied toa projection converting unit 40. The projection converting unit 40calculates a projection image on the basis of the ROI information suchthat data other than that in the ROI is not projected on a projectionregion corresponding to the ROI, and displays the projection image on adisplaying unit 42 through a D/A converter 41.

[0104] Alternatively, the projection converting unit 40 clarifies aprojection image in the ROI by weakening data other than that in the ROIby using weighting factors in a region where the ROI is radiographed,and displays the resultant image on the displaying unit 42.

[0105] In this manner, a blood vessel structure that is difficult tospecify because images overlap on a road map can be easily specified byomitting display of blood vessel structure images overlapping each otheron the road map or weakening its display. Therefore, the operator canquickly move the catheter forward. This makes it possible to shorten theexamination (therapy) time and reduce the dose of radiation.

[0106] [First Modification of Third Embodiment]

[0107] In the third embodiment, an ROI is manually designated. Thismodification uses a biplane type unit capable of observation from twodirections as a radiography unit 61. With this unit, 3D positioncoordinates at which a catheter exists may be calculated on the basis ofthe image coordinates of the distal end of the catheter, which is acharacteristic structure extracted from images in two directions, and anROI centered on the calculated point may be set. As a technique ofextracting an image of the distal end of the catheter, a technique ofdetecting a material having a high absorption coefficient and attachedto the distal end of the catheter, a technique of extracting a portioncorresponding to a time difference, or the like can be used. This makesit possible to automatically set an ROI.

[0108] [Second Modification of Third Embodiment]

[0109] In the first modification of the third embodiment, an ROI isautomatically set by using the radiography unit 61 having the biplanearrangement. However, an ROI can also be automatically set by using asingle-plane X-ray diagnosis apparatus in the same manner as describedabove.

[0110] In this case, the distal end of a catheter is specified on aradiographic image, and the image is backprojected from the specifiedpoint within the image coordinate system. At this time, a blood vesselstructure that intersects a backprojection line is set as a candidatefor the center of an ROI.

[0111] More specifically, a density distribution is searched along thebackprojection line, and a point at which the detected density exceedsthe density of the blood vessel first and a point at which the detecteddensity becomes lower than the density of the blood vessel next arerecognized as points defining a boundary of one blood vessel structure.The midpoint between the detected points is then set as a candidatepoint of the ROI. This operation is repeated on the line to obtain aplurality of candidate points. A similar search is made along a linesegment connecting each candidate point and the center of the ROI in aframe one or a plurality of frames ahead of the current frame. If aregion other than the blood vessel enters the search area, thecorresponding candidate point is canceled. The number of candidatepoints can be decreased by the above operation. In some case, acandidate point cannot be uniquely specified by this method. In such acase, a plurality of ROIs are set. The operator selects a desired ROIfrom the plurality of designated ROIs. This makes it possible tosemi-automatically set an ROI even by using a single-plane X-raydiagnosis apparatus.

[0112] [Third Modification of Third Embodiment]

[0113] In the third embodiment described above, the density of a 3Dblood vessel image is projected. However, the distance from the X-rayfocal point or the detector to the surface of a target region may beprojected. In this case, since pieces of projected information alwaysoverlap, only information having the smallest or largest value isprojected. With this operation, depth information can be added to a 2D.road map, and hence catheter operation is facilitated. This makes itpossible to shorten the examination time and reduce the dose ofradiation.

[0114] [Fourth Modification of Third Embodiment]

[0115] In the third modification of the third embodiment, the distancefrom the boundary of a target region to an X-ray tube 12 or camerasystem 13 is projected and displayed. However, this image may bedisplayed in color and color bar. In addition, depth information at theposition of the ROI in the color bar may be displayed more clearly bydisplaying an arrow or the like.

[0116] [Fifth Modification of Third Embodiment]

[0117] In the third and fourth modifications of the third embodiment,the distance from the boundary of a target region to the X-ray tube 12or camera system 13 is projected and displayed. However, the displaydensity or color may be updated around the current position. Forexample, the display colors are dynamically changed such that thecurrent position is always displayed in the central color of the-colorbar. However, incessant changes in color make it difficult to grasp thestructure of a portion whose depth greatly changes. Alternatively,therefore, the color may be changed on the basis of one or a combinationof some of the following conditions: predetermined time intervals, apredetermined change in depth, a change in projection angle, and achange in projection position. A reset switch or the like may be used tochange the color upon depression of the switch. This makes it possibleto display depth information near an ROI more clearly.

[0118] [Sixth Modification of Third Embodiment]

[0119] In the third, fourth, and fifth modifications of the thirdembodiment, distance information about an overall blood vessel structure(including the axis and other portions) is projected. However, depthinformation is only required to indicate the central axis. For thisreason, only the central axis of the blood vessel is extracted firstfrom a 3D image by a thinning method, and only the extracted centralline is projected as distance information, while density information isprojected for other portions. Note that 3D thinning processing can bebasically performed by extension from 2D to 3D. This makes it possibleto simultaneously observe a conventional road map and depth information.This therefore can provide depth information while preventing confusionof the operator (examiner). Making the projected central line relativelythick will make the displayed image more readable.

[0120] The density information of the projected central line may be setas the boundary of the blood vessel. If this information is displayed onthe axis of the blood vessel, the information is difficult to reachdepending on the density of the road map. However, setting theinformation at the boundary of the blood vessel makes it more readable.This processing can be executed by thinning the road map, making theresultant data correspond to the projected central line, and finding twonearest boundaries in a direction perpendicular to the thinned centralline.

[0121] The present invention is not limited to the above embodiments.Various changes and modifications of the present invention other thanthe respective embodiments can be made in accordance with design and thelike within the technical scope of the invention.

[0122] In each embodiment described above, the coil (occlusive material)is detained. This is an example presented to facilitate theunderstanding of the present invention. Note that the present inventionis effective before and after a change of every circumstance as well asthese therapies and the like.

[0123] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A medical image processing apparatus comprising:a storing unit configured to store first 3D image data corresponding toa first period and second 3D image data corresponding to a secondperiod, the first and second periods defining a period therebetween inwhich a condition of a subject is changed; a 3D subtracting unitconfigured to subtract the first 3D image data from the second 3D imagedata to generate 3D subtraction image data; a pseudo 3D image datagenerating unit configured to generate pseudo 3D image data on the basisof the 3D subtraction image data; and a displaying unit configured todisplay the pseudo 3D image data.
 2. An apparatus according to claim 1,wherein the condition is changed by contrast agent injection operationand/or therapeutic operation.
 3. An apparatus according to claim 2,further comprising: a radiography unit configured to radiograph asubject to obtain multiangle 2D image data, acquire first multiangle 2Dimage data (A) before the therapeutic operation and the contrast agentinjection operation, acquire second multiangle 2D image data (B) beforethe therapeutic operation after the contrast agent injection operation,acquire third multiangle 2D image data (C) after the therapeuticoperation before the contrast agent injection operation, and acquirefourth multiangle 2D image data after the therapeutic operation and thecontrast agent injection operation; a 2D subtracting unit configured tosubtract the first multiangle 2D image data (A) from the secondmultiangle 2D image data (B) to acquire first multiangle 2D subtractionimage data (E), and subtract the third multiangle 2D image data (C) fromthe fourth multiangle 2D image data (D) to acquire second multiangle 2Dsubtraction image data (I); and a reconstructing unit configured toreconstruct the first 3D image data (J) from the first multiangle 2Dsubtraction image data (E) and reconstruct the second 3D image data (N)from the second multiangle 2D subtraction image data (I) said 3Dsubtracting unit subtracting the second 3D image data (N) from the first3D image data (J).
 4. A medical image processing apparatus comprising: aradiography unit configured to radiograph a subject to acquiremultiangle 2D image data, acquire first multiangle 2D image data (A)before therapeutic operation and contrast agent injection operation,acquire second multiangle 2D image data (B) before the therapeuticoperation after the contrast agent injection operation, acquire thirdmultiangle 2D image data (C) after the therapeutic operation before thecontrast agent injection operation, and acquire fourth multiangle 2Dimage data (D) after the therapeutic operation and the contrast agentinjection operation; a 2D subtracting unit configured to subtract thefirst multiangle 2D image data (A) from the second multiangle 2D imagedata (B) to acquire first multiangle 2D subtraction image data (E),subtract the third multiangle 2D image data (C) from the fourthmultiangle 2D image data (D) to acquire second multiangle 2D subtractionimage data (I), and subtract the first multiangle 2D image data (A) fromthe fourth multiangle 2D image data (C) to acquire third multiangle 2Dsubtraction image data (F); a reconstructing unit configured toreconstruct the first 3D image data (J) from the first multiangle 2Dsubtraction image data (E), reconstruct the second 3D image data (N)from the second multiangle 2D subtraction image data (I), and/orreconstruct the third 3D image data (K) from the third multiangle 2Dsubtraction image data (F); and a 3D adding unit configured tothree-dimensionally add the first 3D image data (J) to the third 3Dimage data (K) to acquire the first 3D addition image data (O) and/orthree-dimensionally add the second 3D image data (N) to the third 3Dimage data (K) to acquire the first 3D addition image data (Q).
 5. Amedical image processing apparatus comprising: a radiography unitconfigured to radiograph a subject to obtain multiangle 2D image data,acquire first multiangle 2D image data (A) before therapeutic operationand contrast agent injection operation, acquire second multiangle 2Dimage data (B) before the therapeutic operation after the contrast agentinjection operation, acquire third multiangle 2D image data (C) afterthe therapeutic operation before the contrast agent injection operation,and acquire fourth multiangle 2D image data after the therapeuticoperation and the contrast agent injection operation; a 2D subtractingunit configured to subtract the first multiangle 2D image data (A) fromthe third multiangle 2D image data (C) to acquire first multiangle 2Dsubtraction image data (F) and subtract the second multiangle 2D imagedata (B) from the fourth multiangle 2D image data (D) to acquire secondmultiangle 2D subtraction image data (H); and a reconstructing unitconfigured to reconstruct 3D image data (K) from the first multiangle 2Dsubtraction image data (F) and/or reconstruct 3D image data (M) from thesecond multiangle 2D subtraction image data (H).
 6. A medical imageprocessing apparatus comprising: a radiography unit configured toradiograph a subject to obtain multiangle 2D image data, acquire firstmultiangle 2D image data (A) before therapeutic operation and contrastagent injection operation, acquire second multiangle 2D image data (B)before the therapeutic operation after the contrast agent injectionoperation, acquire third multiangle 2D image data (C) after thetherapeutic operation before the contrast agent injection operation, andacquire fourth multiangle 2D image data after the therapeutic operationand the contrast agent injection operation; a 2D subtracting unitconfigured to subtract the first multiangle 2D image data (A) from thesecond multiangle 2D image data (B) to acquire first multiangle 2Dsubtraction image data (E), subtract the first multiangle 2D image data(A) from the third multiangle 2D image data (C) to acquire secondmultiangle 2D subtraction image data (F), subtract the first multiangle2D image data (A) from the fourth multiangle 2D image data (D) toacquire third multiangle 2D subtraction image data (G), subtract thesecond multiangle 2D image data (B) from the fourth multiangle 2D imagedata (D) to acquire fourth multiangle 2D subtraction image data (H), andsubtract the third multiangle 2D image data (C) from the fourthmultiangle 2D subtraction image data (D) to acquire fifth multiangle 2Dsubtraction image data (I); and a reconstructing unit configured torespectively reconstruct first 3D image data (J), second 3D image data(K), third 3D image data (L), fourth 3D image data (M), and fifth 3Dimage data (N) from the first multiangle 2D subtraction image data (E),the second multiangle 2D subtraction image data (F), the thirdmultiangle 2D subtraction image data (G), the fourth multiangle 2Dsubtraction image data (H), and/or the fifth multiangle 2D subtractionimage data (I).
 7. A medical image processing apparatus comprising: aradiography unit configured to radiograph a subject to obtain multiangle2D image data, acquire first multiangle 2D image data (A) beforetherapeutic operation and contrast agent injection operation, acquiresecond multiangle 2D image data (B) before the therapeutic operationafter the contrast agent injection operation, acquire third multiangle2D image data (C) after the therapeutic operation before the contrastagent injection operation, and acquire fourth multiangle 2D image dataafter the therapeutic operation and the contrast agent injectionoperation; a 2D subtracting unit configured to subtract an arbitrarypair of multiangle 2D image data selected from the first, second, third,and fourth multiangle 2D image data (A-D) in accordance with a userinstruction to acquire multiangle 2D subtraction image data; and areconstructing unit configured to reconstruct 3D image data from themultiangle 2D subtraction image data.
 8. A medical image processingapparatus comprising: a radiography unit configured to radiograph asubject to obtain multiangle 2D image data, acquire first multiangle 2Dimage data (A) before therapeutic operation and contrast agent injectionoperation, acquire second multiangle 2D image data (B) before thetherapeutic operation after the contrast agent injection operation,acquire third multiangle 2D image data (C) after the therapeuticoperation before the contrast agent injection operation, and acquirefourth multiangle 2D image data after the therapeutic operation and thecontrast agent injection operation; a 2D subtracting unit configured tosubtract the first multiangle 2D image data (A) from the secondmultiangle 2D image data (B) to acquire first multiangle 2D subtractionimage data (E), subtract the first multiangle 2D image data (A) from thethird multiangle 2D image data (C) to acquire second multiangle 2Dsubtraction image data (F), subtract the first multiangle 2D image data(A) from the fourth multiangle 2D image data (D) to acquire thirdmultiangle 2D subtraction image data (G), subtract the second multiangle2D image data (B) from the fourth multiangle 2D image data (D) toacquire fourth multiangle 2D subtraction image data (H), and subtractthe third multiangle 2D image data (C) from the fourth multiangle 2Dimage data (D) to acquire fifth multiangle 2D subtraction image data(I); and a reconstructing unit configured to respectively reconstructfirst 3D image data (J), second 3D image data (K), third 3D image data(L), fourth 3D image data (M), and fifth 3D image data (N) from thefirst multiangle 2D subtraction image data (E), the second multiangle 2Dsubtraction image data (F), the third multiangle 2D subtraction imagedata (G), the fourth multiangle 2D subtraction image data (H), and/orthe fifth multiangle 2D subtraction image data (I), and said 3Dsubtracting unit three-dimensionally subtracts an arbitrary pair ofimage data selected from the first 3D image data (J), the second 3Dimage data (K), the third 3D image data (L), the fourth 3D image data(M), and the fifth 3D image data (N) in accordance with a userinstruction.
 9. An apparatus according to claim 1, wherein said pseudo3D image data generating unit generates first pseudo 3D image data fromthe first 3D image data and generates second pseudo 3D image data in thesame line-of-sight direction as the first pseudo 3D image data from thesecond 3D image data, and said displaying unit displays the first andsecond pseudo 3D image data side by side on the same screen.
 10. Anapparatus according to claim 7, wherein said pseudo 3D image datagenerating unit generates first pseudo 3D image data from the first 3Dimage data and generates second pseudo 3D image data in the sameline-of-sight direction as the first pseudo 3D image data from thesecond 3D image data, and said displaying unit displays the first andsecond pseudo 3D image data side by side on the same screen.
 11. Amedical image processing apparatus comprising: a radiography unitconfigured to radiograph a subject to obtain multiangle 2D image data,acquire first multiangle 2D image data (A) before therapeutic operationand contrast agent injection operation, acquire second multiangle 2Dimage data (B) before the therapeutic operation after the contrast agentinjection operation, acquire third multiangle 2D image data (C) afterthe therapeutic operation before the contrast agent injection operation,and acquire fourth multiangle 2D image data (D) after the therapeuticoperation and the contrast agent injection operation; and areconstructing unit configured to reconstruct first 3D image data (A′)from the first multiangle 2D image data (A), reconstruct second 3D imagedata (B′) from the second multiangle 2D image data (B), reconstructthird 3D image data (C′) from the third multiangle 2D image data (C),and/or reconstruct fourth 3D image data (D′) from the fourth multiangle2D image data (D), and said 3D subtracting unit three-dimensionallysubtracts an arbitrary pair of image data selected from the first,second, third, and fourth 3D image data (A′-D′) in accordance with auser instruction.
 12. A medical image processing apparatus comprising: aradiography unit configured to radiograph a subject to obtain multiangle2D image data, acquire first multiangle 2D image data (A) beforetherapeutic operation and contrast agent injection operation, acquiresecond multiangle 2D image data (B) before the therapeutic operationafter the contrast agent injection operation, acquire third multiangle2D image data (C) after the therapeutic operation before the contrastagent injection operation, and acquire fourth multiangle 2D image (D)data after the therapeutic operation and the contrast agent injectionoperation; a reconstructing unit configured to reconstruct first 3Dimage data (A′) from the first multiangle 2D image data (A), second 3Dimage data (B′) from the second multiangle 2D image data (B),reconstruct third 3D image data (C′) from the third multiangle 2D imagedata (C), and reconstruct fourth 3D image data (D′) from the fourthmultiangle 2D image data (D); and an adding unit configured tothree-dimensionally add an arbitrary pair of image data selected fromthe first, second, third, and/or fourth 3D image data (A′-D′) inaccordance with a user instruction.
 13. An X-ray diagnosis apparatuscomprising: an X-ray tube configured to irradiate a subject with anX-ray; an X-ray detection unit configured to detect an X-ray transmittedthrough the subject; a collimater arranged between said X-ray tube andsaid X-ray detection unit and configured to variably limit anirradiation field in which the subject is irradiated with the X-ray; animage data generating unit configured to generate 2D and/or 3D imagedata on the basis of an output from said X-ray detection unit; adisplaying unit configured to display the image data; an ROI settingunit configured to set a region of interest on the displayed image inaccordance with a user instruction; and a controller configured tocontrol said collimater on the basis of a position and size of the setregion of interest so as to adjust the irradiation field to a rangecorresponding to the set region of interest.
 14. An apparatus accordingto claim 1, wherein said apparatus further comprises a mechanismconfigured to change a positional relationship between said X-ray tube,said X-ray detection unit, and said collimator, and said controllercontrols said mechanism on the basis of the position and size of the setregion of interest so as to change the positional relationship betweensaid X-ray tube, said X-ray detection unit, and said collimator.
 15. Anapparatus according to claim 13, wherein said apparatus furthercomprises a mechanism configured to change a positional relationshipbetween said X-ray tube, said X-ray detection unit, and said collimator,and said controller controls said mechanism on the basis of the positionand size of the set region of interest so as to change the positionalrelationship between said X-ray tube, said X-ray detection unit, andsaid collimator.
 16. An apparatus according to claim 13, wherein saidapparatus further comprises a bed configured to lay a subject thereon,and a mechanism configured to change a positional relationship betweensaid X-ray tube, said X-ray detection unit, said collimator, and saidbed, and said controller controls said mechanism on the basis of theposition and size of the set region of interest so as to change thepositional relationship between said X-ray tube, said X-ray detectionunit, said collimator, and said bed.
 17. An X-ray diagnosis apparatuscomprising: an X-ray tube configured to irradiate a subject with anX-ray; an X-ray detection unit configured to detect an X-ray transmittedthrough the subject; an image data generating unit configured togenerate 3D image data on the basis of an output from said X-raydetection unit; a 3D image processing unit configured to generateprojection image data projected in substantially the same direction as aobservation direction of the X-ray diagnosis from the 3D image data; anda display unit configured to display X-ray image data and the projectionimage data side by side on the same screen.
 18. An apparatus accordingto claim 17, wherein said apparatus further comprises a unit configuredto add the X-ray image data and the projection image data uponpositioning the data, and said displaying unit displays addition imagedata of the X-ray image data and the projection image data.
 19. Anapparatus according to claim 17, wherein said 3D image processing unitprojects the 3D image data along projection lines corresponding to raysof light dispersing from an X-ray focal point of said X-ray tube towarda detection surface of said X-ray detection unit.
 20. An apparatusaccording to claim 17, wherein said 3D image processing unit generatesthe projection image data from part of the 3D image data correspondingto a region of interest set in accordance with a user instruction. 21.An apparatus according to claim 20, further comprising a unit configuredto set a plurality of sub-regions of interest with respect to the 3Dimage data, and a unit configured to add the plurality of sub-regions ofinterest to obtain the region of interest.
 22. An apparatus according toclaim 17, wherein said 3D image processing unit comprises a unitconfigured to extract a surface of a target region from the 3D imagedata, a distance calculating unit configured to calculate a distancefrom a projection surface to the surface, and a unit configured toproject the 3D image data on the basis of the calculated distance. 23.An apparatus according to claim 22, wherein said distance calculatingunit includes a unit configured to select a distance associated with asurface which is selected in accordance with a user instruction andlocated near said X-ray tube or said X-ray detection unit when aplurality of surfaces overlap.
 24. An apparatus according to claim 22,wherein said distance calculating unit includes a unit configured toextract a central line of a tubular region from the 3D image data, aunit configured to calculate a distance from a projection surface to thecentral line, and a unit configured to project the 3D image data on thebasis of the calculated distance.
 25. An apparatus according to claim24, wherein said distance calculating unit includes a unit configured toproject only a region located on the central line on the basis of thecalculated distance to obtain first projection image data, and a unitconfigured to project a region other the region located on the centralline to obtain second projection image data, the first projection imagedata being added to the second projection image data.